Beta 2 adrenoceptor antagonists for treating orthostatic hypotension

ABSTRACT

Methods of treating orthostatic hypotension are disclosed. The methods include administering to a subject in need thereof an effective amount of a beta 2 (β2) adrenoceptor antagonist, and in particular, the specific β2 adrenoceptor antagonist, 3-(isopropylamino)-1-[(7-methyl-4-indanyl)oxy]butan-2-ol.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/829,339 filed on May 31, 2013, which is hereby incorporated byreference in its entirety.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under HL071140 awardedby the National Institutes of Health. The government has certain rightsin the invention.

BACKGROUND

The present disclosure relates generally to methods of treatinghypotension, and in particular, orthostatic hypotension. Moreparticularly, the present disclosure relates to methods of treatingorthostatic hypotension in a subject in need thereof by administering aneffective amount of a beta 2 (β2) adrenoceptor antagonist. In oneembodiment, the β2 adrenoceptor antagonist is3-(isopropylamino)-1-[(7-methyl-4-indanyl)oxy]butan-2-ol.

Low blood pressure, or hypotension, occurs when blood pressure duringand after each heartbeat is lower than usual in a subject. Thisphenomena further results in the heart, brain, and other parts of thebody not receiving sufficient blood. For some subjects, hypotension cansignal an underlying problem, for example low blood volume, widening ofblood vessels, anemia, heart problems, or endocrine problems, especiallywhen it drops suddenly or is accompanied by signs and symptoms such as,for example, dizziness or light-headedness; fainting; lack ofconcentration; blurred vision; nausea; cold, clammy, pale skin; rapid,shallow breathing; fatigue; depression; thirst; and the like.

Orthostatic hypotension, also known as postural hypotension, however, isa common phenomenon that can occur briefly in anyone. Orthostatichypotension occurs when a subject's blood pressure suddenly falls whenchanging position, such as standing up or stretching. Medically, it isdefined as a fall in systolic blood pressure of at least 20 mm Hg anddiastolic blood pressure of at least 10 mm Hg when a subject assumes astanding position.

While there is currently no effective drug therapy being used to treatthese quick, common episodes as they typically are not considered lifethreatening, it would be advantageous if treatment was available,particularly for elderly subjects who are subject to falling duringthese episodes or younger patients who suffer from severe forms oforthostatic hypotension. Additionally, it would be beneficial if thistreatment could further be administered to subjects undergoing othertherapies that result in a drop in blood pressure, such as chemotherapy,as well as to subjects who suffer from dizziness or low blood pressuredue to heart arrhythmias or anesthesia.

BRIEF DESCRIPTION

The present disclosure is generally related to methods for preventing,reducing, and/or treating hypotension, particularly orthostatichypotension, or head rush. More particularly, the present disclosurerelates to the use of beta 2 (β2) adrenergic receptor antagonists forpreventing, reducing, and/or treating hypotension. In one particularembodiment, the β2 adrenergic receptor antagonist is3-(isopropylamino)-1-[(7-methyl-4-indanyl)oxy]butan-2-ol, commerciallyavailable as ICI 118,551 from Akzo Nobel N.V. (Amsterdam, Netherlands).

It is well-established that the autonomic nervous system (ANS) isimportant in controlling not only heart rhythm and contraction, but alsothe vasomotor tone and systemic blood pressure (BP). Chronic stimulationof the stellate ganglion can cause hypertension in dogs, suggesting thatelevated sympathetic tone is a cause of hypertension. The importance ofthe sympathetic nervous system in hypertension is further supported byrecent studies that show renal sympathetic denervation can effectivelyreduce BP in subjects with drug-refractory hypertension through thereduction of sympathetic nerve activity and norepinephrine spill over.However, the relationship between sympathetic nerve activity and BP isnot unidirectional because elevated BP may suppress sympathetic nerveactivity through baroreflex mechanisms in humans and in ambulatoryrabbits. While the activation of sympathetic perivascular nerves causesvasoconstriction, the parasympathetic or sensory arm plays an equallyimportant role in blood pressure control through vasodilation.

In addition to its effects on peripheral vascular resistance, theautonomic nervous system also controls heart rate, which impactsdiastolic filling, stroke volume, and hence the systemic BP.Additionally, in the present disclosure, it has been unexpectedlydiscovered that orthostatic hypotension occurs when the stellateganglion nerve activity (SGNA) and vagal nerve activity (VNA)simultaneously terminate at the time of postural change. Moreparticularly, preliminary data demonstrated that the stellate ganglionand vagal nerve do not fire independently of each other, but rather,there is a high degree of coordination between these two nervestructures. This pattern of correlation in part determines thespontaneous occurrences of atrial tachyarrhythmias. Among the activationpatterns, simultaneous sympathovagal discharges are particularlyarrhythmogenic. Given its importance to arrhythmogenesis, it is likelythat the patterns of SGNA-VNA correlation also play a role in BP controlin both physiologic and pathologic conditions. Accordingly, the presentdisclosure is directed to reducing BP fluctuation resulting from thesimultaneous onset and offset of sympathovagal discharge by blockingadrenergic receptors.

Accordingly, in one aspect, the present disclosure is directed to amethod for treating hypotension in a subject in need thereof. The methodcomprises administering a therapeutically effective amount of a β2adrenoceptor antagonist to the subject. In one embodiment, thehypotension to be treated is orthostatic hypotension. In yet anotherembodiment, the hypotension to be treated is anesthesia-relatedhypotension.

In another aspect, the present disclosure is directed to a method fortreating dizziness in a subject in need thereof. The method comprisesadministering a therapeutically effective amount of a β2 adrenoceptorantagonist to the subject.

In another aspect, the present disclosure is directed to a method forreducing blood pressure fluctuation in a subject in need thereof. Themethod comprises administering a therapeutically effective amount of aβ2 adrenoceptor antagonist to the subject.

In another aspect, the present disclosure is directed to apharmaceutical composition comprising a therapeutically effective amountof 3-(isopropylamino)-1-[(7-methyl-4-indanyl)oxy]butan-2-ol and apharmaceutical carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be better understood, and features, aspects andadvantages other than those set forth above will become apparent whenconsideration is given to the following detailed description thereof.Such detailed description makes reference to the following drawings,wherein:

FIGS. 1A-1D depict representative autonomic nerve activity as analyzedin the Examples. FIG. 1A depicts examples of simultaneous sympathovagalco-activation in a Group 1 dog. The asterisk indicates the start ofnerve firing which occurs a few seconds prior to increase in bloodpressure. FIG. 1B depicts the termination of sympathovagal firing of thesame dog as analyzed in FIG. 1A after 68 seconds (not shown) ofcontinuous firing. Note that the end of firing is followed by a sharpdecrease in blood pressure. The VNA is quiescent, but intermittent smallbursts of SGNA (asterisks) were present. FIG. 1C depicts nerve activityof a Group 2 dog; note the separate sympathetic and vagal firing, asmarked by asterisks. SGNA was associated with increased heart rate andBP (dashed arrow). VNA was associated with reduced heart rate and BP.FIG. 1D depicts the solitary sympathetic nerve firing associated withtransient increases in blood pressure. Arrows indicate bradycardia,which are associated with VNA at times when SGNA was inactive. Asterisksshow intermittent SGNA, which are associated with a transient increaseof BP (dashed arrows).

FIGS. 2A-2D depict the evolution of the SGNA-VNA correlation over timein dog #1, which was monitored for over 6 months. FIG. 2A shows that thedog had a linear SGNA-VNA correlation in July. Each dot represents SGNAand VNA activity integrated over 60 seconds. The patterns graduallychanged to L-shaped SGNA-VNA correlation in December. Mean systolicarterial blood pressure and correlation are shown for each graph. Thereis no apparent relationship between the correlation patterns and themean Systolic blood pressure (SBP).

FIGS. 3A-3F depict autonomic nerve activity and postural hypotension asanalyzed in the Examples. FIGS. 3A-3C show orthostatic hypotension indog #1. FIG. 3A shows simultaneous SGNA, VNA and BP recordings; videorecordings were taken during the same time (FIGS. 3B and 3C). The solidline marks the time in the recording that corresponds to FIG. 3B and thedashed line marks the time for FIG. 3C. Note the simultaneoussympathovagal discharge while the dog is lying quietly (FIG. 3B). Thetermination of sympathovagal discharge occurs when the dog stands up(FIG. 3C) and resulted in a large (>20 mmHg) change in BP. FIGS. 3D-3Fdepict nerve activity and postural hypotension of dog #2, which shows nochange in position from FIG. 3E to FIG. 3F. Note the cessation ofsympathovagal discharge at the same time. However, there was only asmall drop in BP (˜10 mmHg) without changes in position.

FIGS. 4A-4B depict circadian variation of the hypotensive (<70 mmHg)episodes as analyzed in the Examples. FIG. 4A shows a representativehypotensive sample. Note that the hypotensive episode occurred afterabrupt termination of sympathovagal discharge. FIG. 4B shows a catalogueof all hypotensive episodes in two different days, one week apart,fitted with a cubic smoothing spline (solid line). The hypotensiveepisodes were defined as a drop of 20 mmHg in BP over no more than 4heart beats. The dashed lines are the point-wise 95% confidenceintervals. There is strong evidence of circadian variation. P<0.001.

FIGS. 5A-5I depict responses to simultaneous termination of SGNA-VNA atbaseline (FIGS. 5A-5C), during carvedilol administration (FIGS. 5D-5F)and during ICI infusion (FIGS. 5G-5I) as analyzed in the Examples.During baseline (FIG. 5A), termination of simultaneous sympathovagaldischarge and change in the dog's posture from lying to sitting (FIGS.5B-5C) resulted in a drop in BP from 110 mmHg to 80 mmHg. This samepattern is seen during carvedilol infusion (FIG. 5D), where terminationof simultaneous firing and postural changes (FIGS. 5E-5F) were followedby a drop in BP from 100 mmHg to 80 mmHg. Note that during ICI infusion(FIG. 5G), there was no change in BP following termination ofsympathovagal firing and postural change (FIGS. 5H-5I).

FIG. 6 depicts the relationship between nerve activity and BP atbaseline in all dogs studied. Each dot represents a 4-hour integratedvalue. Note a large variation of SGNA, VNA and BP among different dogs.Although there is a significant relationship between integrated SGNA andBP (p=0.0478), the effect size was small. The integrated VNA wasnegatively correlated with the BP, but their relationship wasstatistically insignificant (p=0.0648).

FIGS. 7A-7C depict effects of drugs on BP distribution as analyzed inthe Examples. In FIG. 7A, each dot represents an averaged systolic BPover a 4-hour recording period. The dogs were color coded, showingheterogeneous BP distribution among dogs. The BP did not drop below 100mmHg during ICI infusion (arrows). Each dot in FIG. 7B shows the averagesystolic BP over a 1-minute period. Data from all dogs are shown withthe same color. ICI reduced the probability of BP dropping below 100mmHg (arrows). FIG. 7C shows the relationship between integrated SGNA(iSGNA) and integrated VNA (iVNA) at baseline (upper row) and during ICIinfusion (lower row). The response of nerve activities to ICI was highlyheterogeneous. While in some dogs (such as dog #1 and dog #7) the nerveactivity was reduced during ICI infusion as compared with baseline, inother dogs no reduction was observed.

FIGS. 8A-8D depict tyrosine hydroxylase staining of the thoracic vagalnerves. Darker color identifies nerves that stained positively fortyrosine hydroxylase (TH). FIG. 8A shows nerves from a Group 1 dog; notethe strong TH staining (TH+%=41.5%). FIG. 8B is a section from a Group 2dog with 16% TH staining. FIG. 8C is also from a Group 2 dog, but showssubstantially less TH+staining (0.13%). These staining results emphasizethe wide range of TH staining even within the same group of dogs. FIG.8D demonstrates the presence of ganglion cells (arrows) stainingpositively for TH within the thoracic vagal nerve of a Group 1 dog. Theobjective lens used in FIGS. 8A-8D was 10× with a calibration bar of 10μm in length.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described below in detail. Itshould be understood, however, that the description of specificembodiments is not intended to limit the disclosure to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the disclosure as defined by the appended claims.

Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the disclosure belongs. Although any methods andmaterials similar to or equivalent to those described herein can be usedin the practice or testing of the present disclosure, the preferredmethods and materials are described below.

In accordance with the present disclosure, methods have been discoveredthat prevent and protect those subjects suffering from posturalorthostatic hypotension syndrome (POTS), thus preventing fainting,dizziness, and possible falling. In one aspect, the present disclosureis directed to a method for preventing POTS in a subject in needthereof. The method includes administering a therapeutically effectiveamount of a β2-adrenoceptor antagonist.

As used herein, “β2-adrenoceptor antagonist” refers to a high affinityantagonist that is selective for the beta adrenoceptor, and inparticular to the β2 subtype adrenoceptor; that is, that specificallybinds to a β2-adrenoceptor, also referred to herein as β2 adrenergicreceptor.

As used herein, in the most general form, “specific binding”, “bindsspecifically to”, “specific to/for” or “specifically recognizes” referto the ability of the antagonist to discriminate between theβ2-adrenoceptor and an unrelated receptor, as determined in accordancewith methods known in the art, such as, for example, selectivityprofiling using cell based assays (e.g., Ricerca cell-based screen).

As used herein, “binding affinity” refers to the strength of the sumtotal of non-covalent interactions between a single binding site of amolecule and its binding partner. Unless indicated otherwise, as usedherein, “binding affinity” refers to intrinsic binding affinity whichreflects a 1:1 interaction between members of a binding pair (e.g., anantagonist and receptor). The dissociation constant “KD” is commonlyused to describe the affinity between a molecule (such as an antagonist)and its binding partner (such as a receptor), i.e., how tightly a ligandbinds to a particular protein. Ligand-protein affinities are influencedby non-covalent intermolecular interactions between the two molecules.Affinity can be measured by common methods known in the art, including,for example, surface plasmon resonance or isothermal titrationcalorimetry.

As used herein, “hypotension” refers to a condition that occurs whenblood pressure during and after each heartbeat is lower than usual in asubject. More specifically, hypotension refers to a fall in systolicblood pressure of at least 20 mm Hg and diastolic blood pressure of atleast 10 mm Hg. Hypotension can be the result of, for example,dehydration, severe bleeding, organ inflammation, heart disease (e.g.,myocarditis, aortic stenosis, pericarditis, pulmonary embolism,bradycardia), medication-induced hypotension (e.g., anesthesia,chemotherapy), vasovagal reaction, orthostatic hypotension, micturitionsyncope, adrenal insufficiency (e.g., Addison's Disease), septicemia,anaphylaxis, and the like. In particular embodiments, the subjectsuffers from episodes of orthostatic hypotension.

As used herein, “severe bleeding” refers to a condition in which asubject loses greater than 15% of total blood volume, including greaterthan 20% of total blood volume, including greater than 30% of totalblood volume, and including greater than 40% of total blood volume.

As used herein, “elderly subject”, refers to a subject of at least 45years of age, including at least 50 years of age, including at least 55years of age, including at least 60 years of age, including at least 65years of age, including at least 70 years of age, including at least 75years of age, including at least 80 years of age, further including fromabout 55 years of age to about 80 years of age.

As used herein, “susceptible” and “at risk” refer to having littleresistance to a certain disease, disorder or condition, and inparticular, to hypotension, including being genetically predisposed,having a family history of, and/or having symptoms of the disease,disorder or condition.

All combinations of method or process steps as used herein can beperformed in any order, unless otherwise specified or clearly implied tothe contrary by the context in which the referenced combination is made.

DETAILED DESCRIPTION

In accordance with the present disclosure, methods have been discoveredthat surprisingly allow for the prevention, reduction, minimization,and/or treatment of hypotension, and hypotension episodes. Particularly,antagonists that specifically bind to the β2-adrenoceptor areadministered, inhibiting adrenergic receptor activation. This inhibitionreduces blood pressure fluctuation such as caused by the simultaneousonset and offset of sympathovagal discharge. The methods provide forprotection from hypotension episodes that can lead to fainting,dizziness, and possible falling to subjects in need thereof.

Methods of Administering β2-Adrenoceptor Antagonists

The methods of the present disclosure generally include theadministration of one or more beta-adrenoceptor antagonists, and inparticular, β2-adrenoceptor antagonists, to a subject in need thereof toprevent/minimize/control blood pressure fluctuations, and in particular,hypotension episodes due to sudden blood pressure drop. Particularly,the methods of the present disclosure canprevent/minimize/reduce/control/treat hypotension, such as orthostatichypotension, in subjects in need thereof; that is, bypreventing/minimizing/controlling blood pressure fluctuations, themethods can prevent/reduce/control/treat hypotension episodes, therebypreventing/controlling/reducing/treating symptoms of the episodesincluding fainting, dizziness, lightheadedness, and possible falling.

Beta-adrenoceptors are coupled to the stimulatory G protein. The alphasubunit of the G protein activates adenylyl cyclase, which catalyzes theproduction of cyclic adenosine monophosphate (cAMP). In the lung, cAMPcauses a decrease in the intracellular calcium concentration and, viaactivation of protein kinase A, both inactivates myosin light chainkinase and activates myosin light chain phosphatase. In addition, β2adrenoceptors open large conductance calcium-activated potassiumchannels and thereby tend to hyperpolarize airway smooth muscle cells.The combination of decreased intracellular calcium, increased membranepotassium conductance, and decreased myosin light chain kinase activityleads to smooth muscle relaxation and bronchodilation. Accordingly, bybinding to β2 adrenoceptors, the methods of the present disclosure canprevent/minimize/control blood pressure fluctuations, furtherpreventing/reducing/controlling/treating hypotension episodes ascompared to subjects that are not administered the β2 adrenoceptorantagonist.

The β2 adrenoceptor antagonist described below in detail and used in themethods of the present disclosure can be administered to a subset ofsubjects in need of preventing/minimizing/controlling blood pressurefluctuations. Some subjects that are in specific need ofrestored/maintained blood pressure levels may include subjects who aresusceptible to, or at elevated risk of, experiencing hypotensionepisodes, including subjects susceptible to, or at elevated risk of,dehydration, severe bleeding, organ inflammation, heart disease (e.g.,myocarditis, aortic stenosis, pericarditis, pulmonary embolism,bradycardia), anesthesia, chemotherapy, vasovagal reaction, orthostatichypotension, micturition syncope, adrenal insufficiency, septicemia,anaphylaxis, and the like. Particularly, the method can be administeredto elderly subjects who may be more likely to fall due to a hypotensionepisode. In one particular embodiment, the methods can be administeredto a subject who has, or is susceptible to, or at elevated risk of,orthostatic hypotension. Subjects may be susceptible to, or at elevatedrisk of, experiencing hypotension episodes/situations due to familyhistory, age, environment, and/or lifestyle. Based on the foregoing,because some of the method embodiments of the present disclosure aredirected to specific subsets or subclasses of identified subjects (thatis, the subset or subclass of subjects “in need” of assistance inaddressing one or more specific conditions noted herein), not allsubjects will fall within the subset or subclass of subjects asdescribed herein for certain diseases, disorders or conditions.

The β2 adrenoceptor antagonist can be administered alone in a suitablepharmaceutical formulation (i.e., no other active compound) or as acomponent of a suitable pharmaceutical formulation comprising theantagonist in combination with another active compound. Additionally,the β2 adrenoceptor antagonist, alone or in combination with anotheractive compound, may be used in the manufacture of one or moremedicaments. The pharmaceutical formulations may include one or morepharmaceutically acceptable carriers as are known in the art. As usedherein, the phrase “pharmaceutically acceptable” refers to thoseligands, materials, formulations, and/or dosage forms which are, withinthe scope of sound medical judgment, suitable for use in contact withthe tissues of human beings and animals without excessive toxicity,irritation, allergic response, or other problem or complication,commensurate with a reasonable benefit/risk ratio. The phrase“pharmaceutically acceptable carrier”, as used herein, refers to apharmaceutically acceptable material, formulation or vehicle, such as aliquid or solid filler, diluent, excipient, solvent or encapsulatingmaterial, involved in carrying or transporting the active compound fromone organ or portion of the body, to another organ or portion of thebody. Each carrier must be “acceptable” in the sense of being compatiblewith the other components of the formulation and not injurious to thesubject. Lyophilized formulations, which may be reconstituted andadministered, are also within the scope of the present disclosure.

Pharmaceutically acceptable carriers may be, for example, excipients,vehicles, diluents, and combinations thereof. For example, where theformulations are to be administered orally, they may be formulated astablets, capsules, granules, powders, or syrups; or for parenteraladministration, they may be formulated as injections (intramuscular,subcutaneous, intramedullary, intrathecal, intraventricular,intraperitoneal, intravenous), drop infusion preparations, orsuppositories. These formulations can be prepared by conventional means,and, if desired, the active compound (i.e., β2 adrenoceptor antagonists)may be mixed with any conventional additive, such as an excipient, abinder, a disintegrating agent, a lubricant, a corrigent, a solubilizingagent, a suspension aid, an emulsifying agent, or a coating agent.

β2 Adrenoceptor Antagonists

One particularly suitable β2 adrenoceptor antagonist is3-(isopropylamino)-1-[(7-methyl-4-indanyl)oxy]butan-2-ol (available asICI-118,551 from Akzo Nobel N.V. (Amsterdam, Netherlands). ICI-118,551is a selective β2 adrenoceptor antagonist, binding to the β2 subtypewith at least 100 times greater affinity than β1 or β3, the two otherknown subtypes of the beta adrenoceptor. Other suitable β2 adrenoceptorantagonists include, for example, salbutamol, levosalbutamol,terbutaline, pirbuterol, procaterol, clenbuterol, metaproterenol,fenoterol, bitolterol mesylate, ritodrine, isoprenaline, salmeterol,formoterol, bambuterol, clenbuterol, indacaterol, and combinationsthereof (chemical structures shown in Table 1 below).

TABLE 1 Common Name IUPAC Name Chemical Structure Salbutamol(RS)-4-[2-(tert- butylamino)-1- hydroxyethyl]-2- (hydroxymethyl) phenol

Terbutaline (RS)-5-[2-(tert- butylamino)-1- hydroxyethyl]benzene-1,3-diol

Isoprenaline (RS)-4-[1-hydroxy-2- (isopropylamino)ethyl]benzene-1,2-diol

Levosalbutamol 4-[(1R)-2-(tert- butylamino)-1- hydroxyethyl]-2-(hydroxymethyl)phenol

Metaproterenol (RS)-5-[1-hydroxy-2- (isopropylamino)ethyl]benzene-1,3-diol

Pirbuterol (RS)-6-[2-(tert- butylamino)-1- hydroxyethyl]-2-(hydroxymethyl)pyridin- 3-ol

Procaterol (±)-(1R,2S)-rel-8- Hydroxy-5-[1-hydroxy-2-(isopropylamino)butyl]- quinolin-2(1H)-one

Clenbuterol (RS)-1-(4-Amino-3,5- dichlorophenyl)-2-(tert-butylamino)ethanol

Fenoterol (RR,SS)-5-(1-hydroxy-2- {[2-(4-hydroxyphenyl)-1-methylethyl]amino}ethyl) benzene-1,3-diol

Bitolterol mesylate (RS)-[4-(1-Hydroxy-2- tert-butylamino-ethyl)- 2-(4-methylbenzoyl)oxy- phenyl] 4-methylbenzoate

Ritodrine 4-(2-((1R,2S)-1-hydroxy- 1-(4- hydroxyphenyl)propan-2-ylamino)ethyl)phenol

Salmeterol (RS)-2-(hydroxymethyl)- 4-{1-hydroxy-2-[6-(4- phenylbutoxy)hexylamino]ethyl}phenol

Formoterol rac-(R,R)-N-[2-hydroxy- 5-[1-hydroxy-2-[1-(4-methoxyphenyl)propan- 2-ylamino]ethyl] phenyl]formamide

Bambuterol (RS)-5-[2-(tert- butylamino)-1- hydroxyethyl]benzene-1,3-diyl bis(dimethylcarbamate)

Indacaterol (R)-5-[2-[(5,6-Diethyl- 2,3-dihydro-1H-inden-2- yl)amino]-1-hydroxyethyl]-8- hydroxyquinolin-2(1H)- one

Actual dosage levels of the β2 adrenoceptor antagonist in apharmaceutical formulation for use in the methods of the presentdisclosure may be varied so as to obtain an amount of the β2adrenoceptor antagonist that is effective to achieve the desiredtherapeutic response or benefit for a particular subject, formulation,and/or mode of administration. More particularly, as used herein, thephrase “therapeutically effective amount” of the β2 adrenoceptorantagonist used in the methods of the present disclosure refers to asufficient amount of a β2 adrenoceptor antagonist to treat hypotensionas defined herein, at a reasonable benefit/risk ratio applicable to anymedical treatment. It can be understood, however, that the total dailyusage of the β2 adrenoceptor antagonist and pharmaceutical formulationsincluding the β2 adrenoceptor antagonists for use in the methods of thepresent disclosure can be decided by the attending physician within thescope of sound medical judgment. The specific therapeutically effectivedose level for any particular subject can depend upon a variety offactors including the hypotension episode being treated and the severityof the episode; activity of the specific β2 adrenoceptor antagonistemployed; the specific pharmaceutical formulation employed; the age,body weight, general health, sex and diet of the subject; the time ofadministration, route of administration, and rate of excretion of thespecific β2 adrenoceptor antagonist employed; the duration of thetreatment; drugs used in combination or coincidental with the specificβ2 adrenoceptor antagonist employed; and like factors well-known in themedical arts. For example, it is well within the skill of the art tostart doses of the β2 adrenoceptor antagonist at levels lower thanrequired to achieve the desired therapeutic effect and to graduallyincrease the dosage until the desired effect is achieved.

In some embodiments, the β2 adrenoceptor antagonist can be administeredto a subject in need thereof in an amount ranging from about 1 μg/kgtotal body weight of the subject to about 5 μg/kg total body weight ofthe subject per hour for a period of about 7 days. In one embodiment,the methods of the present disclosure include administering to a subjectin need thereof an amount of about 3.1 μg/kg total body weight of thesubject per hour for a period of about 7 days. In some embodiments, theβ2 adrenoceptor antagonist can be administered to a subject in needthereof in amounts of from about 5 μg to about 30 μg, including about 10μg, per hour for a period of about 7 days. In particular embodiments,the β2 adrenoceptor antagonist can be administered orally to a subjectin need thereof in amounts of from about 10 mg to about 40 mg, andincluding from about 15 mg to about 35 mg, at regular intervalsincluding every 2 hours, including every 4 hours, including every 8hours, including every 12 hours, including every 24 hours, and includingevery 48 hours. If administered as a daily dosage of β2 adrenoceptorantagonists or pharmaceutical formulation including the β2 adrenoceptorantagonists, the β2 adrenoceptor antagonists or pharmaceuticalformulation including the β2 adrenoceptor antagonists may be in the formof a single dosage or may be in the form of two dosages, three dosages,four dosages or more to be administered two or more times during theday.

It should be understood that the pharmaceutical compositions of thepresent disclosure can further include additional known therapeuticagents, drugs, modifications of the β2 adrenoceptor antagonists intoprodrugs, and the like for alleviating, mediating, preventing, andtreating hypotension.

The disclosure will be more fully understood upon consideration of thefollowing non-limiting Examples.

EXAMPLES

Protocol 1: Ambulatory Monitoring of Autonomic Nerve Activities and BP

Eight mongrel dogs (4 male, weighing 20-30 kg) were used in thisExample. Left thoracotomy was performed through the first intercostalspace for the implantation of a D70-CCTP radiotransmitter manufacturedby the Data Sciences International (DSI, St Paul, Minn.). The first pairof bipolar electrodes was inserted beneath the nerve sheath of the leftstellate ganglion. A second pair of bipolar leads was attached to theleft thoracic vagal nerve at a level of 4 to 5 cm above the aortic arch.The third lead, a catheter with a pressure sensor, was inserted directlyinto the subclavian artery for blood pressure (BP) recording. Thetransmitter and ground wires were inserted into a subcutaneous pocket.The chest wall was then closed.

After 2 weeks of recovery, the radiotransmitter was turned on to recordnerve signals and BP at baseline. The pre-implantation BP was calibratedagainst the ambient pressure in the vivarium. There was a 12-hourdaylight cycle in the vivarium staring at 7 AM each day. After thebaseline (stellate ganglion nerve activity (SGNA), vagal nerve activity(VNA), and BP) recordings, the dogs were given oral carvedilol, 12 mgtwice daily for a week. The drugs were then washed out for a week andbaseline recordings were re-collected. The dogs were brought back to thesterile surgical suite for minor surgery that included subcutaneousimplantation of a 2-ml osmotic pump (model 2ML1) manufactured by AlzetInc. (Cupertino, Calif.). The pump contained 2 ml of ddH₂O and 18 mg ofICI-118,551 (ICI). The pump is designed to empty its contents over 7days at a rate of 10 μl/hr. Therefore, the infusion rate was 3.1μg/kg/hr for a 30 kg dog. The infusion rate at which half theβ₂-receptors are saturated has been reported to be 2 μg/kg in beagles.The data collected at days 6-7 of the infusion were used for analyses. Aweek after completing this stage of drug infusion, the dogs wereeuthanized. The left stellate ganglion and the left thoracic vagalnerves were then harvested for histological and immunohistochemicalanalyses.

Protocol 2: Sympathetic Component in the Thoracic Vagal Nerve andSimultaneous Sympathovagal Discharges

Because the results of Protocol 1 showed significant blood pressurefluctuations associated with simultaneous sympathovagal discharges, itwas hypothesized that the amount of sympathetic nerve fibers within thethoracic vagal nerve in part determined whether the dogs hadsimultaneous sympathovagal discharges and were prone to BP fluctuations.Therefore, dogs were chosen from previous studies that had bothhistological materials and nerve recordings available for the instantanalysis. In addition to dogs from Protocol 1, 12 additional dogs thatunderwent baseline recordings of the SGNA and VNA using a DSI D70-EEEradiotransmitter were included. After 2-3 weeks of recovery after thesurgical implantation of the DSI transmitters, baseline nerve activitieswere recorded while the dogs were ambulatory. At the end of theexperiments, the left thoracic vagal nerves of those dogs were harvestedfor immunohistochemical studies.

Data Analyses

Nerve Activity Analyses

Nerve activities were analyzed both manually and with assistance ofcomputerized methods as set forth in Shen et al., “Chronic low-levelvagus nerve stimulation reduces paroxysmal atrial tachyarrhythmias inambulatory canines by inducing structural and functional remodeling ofthe left stellate ganglion,” Heart rhythm: the official journal of theHeart Rhythm Society. 2011:8: S502, incorporated herein by reference tothe extent it is consistent herewith. The nerve activities wereintegrated minute-by-minute. Because BP recordings are prone to motionartifacts, the data of all dogs included in Protocol 1 was manuallyreviewed and the first 10 noise-free minutes of each hour were selectedfor analyses. The mean BP was also analyzed minute-by-minute during thesame period. The SGNA was plotted against the VNA on an XY graph tovisualize the patterns of activation. Pearson correlation coefficientsbetween these two nerve activities were calculated. The data obtainedfrom the manual analyses were subjected to further statistical analysesas described below.

Immunocytochemical Staining

The left thoracic vagal nerves (N=20) were fixed with 4% formalin for45-60 minutes before transfer to 70% ethyl alcohol. The nerves wereembedded in paraffin and 5 μm thick cross sections were cut and stainedwith tyrosine hydroxylase for sympathetic (adrenergic) nerves. Theprograms Adobe Photoshop CS5.1 and Magic Wand were used to localize theTH positive portions and calculate their cross sectional areasrespectively according to the method described in Onkka et al.,“Sympathetic nerve fibers and ganglia in canine cervical vagus nerves:Localization and quantitation,” Heart rhythm: the official journal ofthe Heart Rhythm Society. 2013:10:585-591, incorporated herein byreference to the extent it is consistent herewith. The cross-sectionalarea of each vagus nerve was then compared with the SGNA-VNA correlationcoefficient at baseline.

Statistical Analyses

Data were summarized as mean±standard deviation and ranges forcontinuous variables and percentages for binary variables weredetermined Parameter estimates were expressed as point estimates and 95%confidence intervals (CI). To determine the relationship between BP,heart rate (HR) and ANS activities, 1-minute and 4-hour averages foreach dog were calculated on each day of data collection starting atmidnight. Pearson correlation coefficients between SGNA and VNA werealso calculated within each 4-hour interval. To analyze data from anygiven individual dog, multiple linear regression with systolic BP as thedependent variable and ANS activities as the independent variables basedon 1-minute average data were used. To analyze data from all dogs andthe 4-hour average data, a random effects model with dog as the randomeffect was used with the same dependent and independent variables, plusHR and the Pearson correlation coefficient as additional independentvariables. Random effects models were also used to compare the effectsof the drugs against baseline on BP, each of the ANS activities, and theproportion of hypotensive episodes (average systolic arterial pressure(SAP)<100 mmHg) using data from all dogs, which included the maineffects of drug and the six 4-hour intervals and their interactions. Acubic smoothing spline was also used to fit BP versus hour for one dog.Statistical analysis was performed with IBM SPSS Statistics 19 (Armonk,N.Y.) and SAS version 9.3 (SAS Institute Inc., Cary, N.C.). A two-sidedp value of ≤0.05 was considered statistically significant.

Results

Protocol 1: Ambulatory Monitoring of Autonomic Nerve Activities and BP

Relationship Between Autonomic Nerve Activity and BP

Each dog was monitored for an average of 10 weeks (range 6 to 21 weeks)during which SGNA, VNA and BP were intermittently collected. Aspreviously reported, there are two basic patterns of nerve activity. Inthe first pattern (termed “Group 1” in that report), the SGNA and VNAactivate simultaneously (FIGS. 1A and 1B). A plot of integrated stellateganglion nerve activity (iSGNA) versus integrated vagal nerve activity(iVNA) gives a linear pattern (FIG. 2A). Five of the eight dogsdemonstrated Group 1 firing upon baseline recording. The SGNA-VNAcorrelation is important in BP control. In general, simultaneoussympathovagal firing (which only occurred in Group 1 dogs) wasassociated with a higher mean BP, but incongruously, more extreme dropsin BP at the time of simultaneous sympathovagal termination. BP is aproduct of heart rate, stroke volume and total peripheral vascularresistance. Because the stroke volume depends in part on diastolicfilling, an abrupt increase or decrease in heart rate may decrease orincrease stroke volume, respectively. The beat-to-beat variation inblood pressure and nerve activity is therefore complex, as illustratedby FIGS. 1A-1D.

FIG. 1A shows a Group 1 dog with a baseline BP ranging from 75 to 100mmHg and heart rate averaging 162 bpm. At the start of the simultaneouslow amplitude sympathovagal discharge (asterisk), the BP started toincrease rapidly. Abrupt increase in BP (dashed arrow) was associatedwith sustained and large amplitude simultaneous sympathovagal dischargeswithout apparent initial increase in HR, probably due to a largeparasympathetic tone provided by vagal nerve. (The BP dropped after thedashed arrow with associated slowing of the heart rate to 132 bpm, whichcould be a response to increased vagal activity.) FIG. 1B shows thatafter 68 seconds of continuous sympathovagal discharge, the nerveactivity abruptly and simultaneously terminated, which was followed by arapid drop in BP to as low as 65 mmHg systolic and 45 mmHg diastolic(black arrow) and tachycardia. The BP then gradually recovered, assistedby low amplitude intermittent SGNA (asterisks). The abrupt terminationof sympathovagal discharge and subsequent drop in BP, followed bygradual recovery, was observed in all Group 1 dogs. The termination ofvagal nerve discharge resulted in an abrupt increase in heart rate thattransiently reduced stroke volume by decreasing diastolic ventricularfilling. In addition, a simultaneous loss of sympathetic support of theperipheral vascular resistance contributed to the abrupt BP reduction.The persistent increase in heart rate and intermittent SGNA activity(asterisks in FIG. 1B) led to gradual increase in BP after thehypotensive episode. An additional factor in the abrupt BP reduction maybe due to coincidental change of posture, as presented below.

The second pattern of nerve activity (Group 2), where SGNA and VNAactivate separately, is shown in FIG. 1C. Note that the independentactivation of SGNA (asterisk, first line) was associated with elevatedBP (dashed arrow) while VNA (asterisk, second line) was associated witha lower mean arterial BP and HR. This represents the classic baroreflexresponse with VNA excitation and reduction of SGNA resulting in a rapidnormalization of BP. FIG. 1D shows a second dog in which SGNA and VNAactivated separately—here the vagus nerve activates alone during thefirst eight seconds of the recording. This activation was associatedwith bradycardia (black arrow). The sympathetic bursts were lowamplitude (asterisks) in the beginning and were associated with briefincreases in HR (dashed arrows) and BP. This was followed by a largeincrease of SGNA and a simultaneous drop of BP. Complete cessation ofSGNA and continuous VNA was associated with bradycardia (second blackarrow). In this case, bradycardia resulted in SGNA excitation withepisodic increase in the BP and heart rate. However, the persistent VNAexcitation (particularly without low-amplitude SGNA excitation)eventually lead to bradycardia.

Changing Sympathovagal Correlation

A previous study that monitored canines for approximately 2 months,suggested that the sympathovagal correlation is static. However,recordings done in the present Examples over a longer time frame (5-6months) demonstrated that patterns of sympathovagal correlation evolveover time. This is best illustrated by dog #1 that was monitored over 6months, as shown in FIGS. 2A-2D. This dog started out during themonitoring period (July) as a Group 1 dog (FIG. 2A). At that time, thedog was 6 months old and weighed 30.1 kg. Slowly, over months, heevolved into a Group 2 dog (FIGS. 2B-2D). The dog's weight increased to40.3 kg in December. iSGNA and iVNA dropped drastically in December.There were increasing SGNA at the time when VNA was silent. Thisnonlinear relationship between SGNA and VNA indicates a complexinteraction between SGNA and VNA. Other dogs stayed in the same groupthroughout the recording, although the patterns of correlation changedslightly over time. Particularly, a linear regression model showed thatthe VNA was negatively associated with BP (p=0.0297), while SGNA waspositively (but insignificantly) associated with BP (p=0.0544) in July,when there was linear sympathovagal correlation. The SGNA was positivelycorrelated with BP (p=0.0213) in August, but the VNA no longer hadsignificant effects on BP (p=0.4776). No significant relationshipbetween SGNA and BP or between VNA and BP was found during November inthis dog (Group 2 state). For all dogs studied, each mV-s increase ofiSGNA was associated with a 0.04580 mmHg increase in BP (p=0.0478). EachmV-s increase of iVNA was associated with an insignificant decrease inBP of −0.05484 mmHg (p=0.0648). Heart rate (p=0.9991) and the SGNA-VNAcorrelation coefficient (p=0.1294) were not associated with BP changesusing analyses summarized by 4-hour intervals. However, as reported inthe previous section, instantaneous changes in BP may occur on a shortertime scale and therefore were not reflected in the BP or ANS averageover one minute.

Abrupt Hypotensive Episodes

As shown in FIG. 1B, abrupt cessation of simultaneous sympathovagaldischarges seen in Group 1 dogs was associated with an abrupt drop inBP. To determine if these episodes were related to postural changes,video cameras were installed in the dog kennel and monitored nerveactivity, BP and video simultaneously. Several patterns of behavioremerged as is shown in FIGS. 3A-3F. The first pattern is illustrated inFIGS. 3A-C. FIG. 3A shows simultaneous firing of the canine'ssympathetic and vagal nerves. The solid line indicates the time thevideo in FIG. 3B was captured; dashed line is the time FIG. 3C wascaptured. Note that the dog was lying down during simultaneoussympathovagal discharge (FIG. 3A). Abrupt termination of the nervedischarges coincided with a change in posture from lying to sitting up(FIGS. 3B-3C). This was accompanied by an abrupt drop in the meanarterial pressure from 80 mmHg to 60 mmHg, a dramatic narrowing of thepulse pressure and an acceleration of HR. The video imaging in threedogs was collected and analyzed a total of 1000 episodes of abruptsimultaneous termination of sympathovagal discharges. Among theseepisodes, 390 were associated with sudden movement, such as standing upor starting to jump. In some episodes, it appeared that the dog wasaroused (FIG. 3A). The second pattern of behavior is illustrated inFIGS. 3D-3E from a different dog. The dog was lying quietly on the floorand remained lying down during both the simultaneous sympathovagaldischarges (solid line) and after the abrupt termination of the firing(dashed line). Note in FIG. 3D the mild drop in BP (from 110 mmHg to 100mmHg, without narrowing of the pulse pressure) and tachycardia after thetermination of sympathovagal discharges. These findings suggest thatabrupt termination of sympathovagal discharge is the primary reason fortransient hypotension and tachycardia. More dramatic changes in BP(hypotension associated with a narrow pulse pressure) occur when the dogterminated the sympathovagal discharge and concomitantly changedposture, possibly at the time of awakening (orthostatic hypotension).

It is well-established that cardiac physiology has a circadian rhythm.In normal subjects, sympathetic tone is highest during the day andlowest at night when parasympathetic tone dominates. Likewise, arterialblood pressure is lowest overnight (about 10-20% lower than during theday) with peaks in pressure early in the morning after waking and againin late afternoon/early evening. Given the evidence in the above datathat the offset of sympathovagal firing predicts hypotensive episodes,it is believed that the periods of hypotension may also have a circadianrhythm. FIGS. 4A and 4B show the circadian variation of the hypotensiveepisodes. FIG. 4A shows an example of extreme hypotension in the samedog as in FIGS. 1A-1D. The BP dipped to as low as 20 mmHg. Thedistribution of similar episodes (drop in pressure of 20 mmHg over 4beats) throughout the day were manually analyzed and a significant(p<0.0001) circadian variation of the hypotensive episodes associatedwith sympathovagal termination was found (FIG. 4B).

Effects of Drugs on Nerve Activity and BP

The importance of sympathetic firing as it relates to large drops inblood pressure, led to a hypothesis that blocking sympathetic tonethrough a non-selective β-adrenoceptor antagonist such as carvedilol, ora specific β2-adrenoceptor antagonist, such as ICI, may decrease thefrequency and severity of hypotensive episodes. The baseline BP was125.60 (95% CI: 117.77 to 133.44) mmHg, which was insignificantlyreduced by carvedilol to 124.8 (95% CI: 116.63 to 132.97) mmHg(p=0.6788), but was significantly increased to 133.00 (95% CI: 124.85 to141.14) mmHg (p=0.0001) after 7 days of ICI infusion. The iSGNAimmediately before drug was 209.40 (95% CI: 163.12 to 255.68) mV-s,which was significantly increased by carvedilol to 258.47 (95% CI:207.20 to 309.75) mV-s (p=0.0087) and by ICI to 281.23 (95% CI: 230.30to 332.16) mV-s (p=0.0001). The iVNA immediately before drug was 192.96(95% CI: 130.58 to 254.62) mV-s, which was insignificantly decreased bycarvedilol (186.68 mV-s, 95% CI: 122.83 to 250.53, p=0.6433), but wassignificantly increased by ICI to 220.18 (95% CI: 156.46 to 283.90) mV-s(p=0.0293). These findings indicate the ICI significantly increasedSGNA, VNA and the BP. FIGS. 5A-5I shows examples of a canine at baseline(FIGS. 5A-5C), during carvedilol administration (FIGS. 5D-5F) and duringICI infusion (FIGS. 5G-5I), respectively. Note as in FIGS. 3A-3F,simultaneous sympathovagal withdrawal was followed by hypotension bothat baseline and during carvedilol administration. However, simultaneouscessation of sympathovagal discharge during ICI infusion was notfollowed by hypotension.

The relationship between SGNA, VNA and BP for all eight dogs at baselineis illustrated in FIG. 6. Each dot represents four hours of integratednerve activity and the corresponding mean systolic blood pressure. Notethat there is significant heterogeneity among dogs; this likely, inpart, reflects the differences in group status. Dogs 1, 4 and 7 in thegraph have the lowest mean SBP and were all Group 1 dogs; whereas thedogs with the highest SBP (5, 8) were Group 2. FIGS. 7A-7C illustratethe relationship between SGNA, VNA and BP during baseline, carvediloland ICI infusion across all eight dogs. In FIG. 7A, each dot representsthe average of 4 hours of integrated nerve activity; in FIG. 7B, eachdot is one minute of integrated nerve activity. The line is drawn tomark 100 mmHg. Note the substantial increase in mean systolic BP betweenbaseline and ICI recordings, but not between baseline and carvedilol inFIG. 7A. The mean BP (calculated over 4 hour intervals) during ICIinfusion did not dip lower than 110 mmHg in any dog (arrows). In FIG.7B, which represents the minute-by-minute data, the number ofhypotensive episodes (defined as mean systolic pressure <100 mmHg in onemin) were calculated for each dog. Each dot represents mean systolic BPover one minute. The percentage of hypotensive episodes during baselinewas 7.1%; after carvedilol, 7.8% (p=0.7475) and after ICI, 1.3%(p=0.0110). These data show that ICI, but not carvedilol, significantlyreduced hypotensive episodes. FIG. 7C shows the SGNA-VNA plots for eachdog during baseline (row 1) and ICI infusion (row 2). Note the variedresponse to ICI infusion among all eight dogs. The absence of consistentresponse of the autonomic nervous system discharges suggests that ICI'seffect on blood pressure occurs via modulation of the vascularβ2-adrenoceptors and not through its effect on the cardiac autonomicnervous system.

Protocol 2: Thoracic Vagal Nerve Structure and Sympathovagal Correlation

The baseline nerve activity patterns were analyzed and the r values forsympathovagal correlation were determined in each of the 20 dogs. TheSGNA-VNA correlation (r) averaged 0.61, SD=0.30 (range 4E-4 to 0.78).TH-positive components were present in the thoracic VN and accounted foran average of 14%, SD=10% (range 0.13% to 43.7%) of the cross sectionalarea (FIGS. 8A-8D: brown indicates areas of positive staining). Therewas only a weak positive correlation (Pearson correlation=0.17,p<0.0001) between r value and the percentage of TH-positive areastaining. These findings, as well as that observed in FIGS. 2A-2D,suggest that the sympathovagal correlation, and hence the orthostasis,is determined both by the amount of TH-positive nerve structures in thevagal nerve and the physiological status of the dogs.

Discussion

Autonomic Nerve Activity and Postural Hypotension

The primary finding of this Example is that the simultaneous termination(offset) of SGNA and VNA may be associated with transient, but oftendramatic, postural hypotension (>20 mmHg over 4 heart beats). Similar tothat found in human subjects with postural hypotension syndrome (POTS),the offset hypotensive episodes in the dogs occurred more often in themorning than other times of the day. The mechanism of hypotension causedby cessation of simultaneous sympathovagal discharges is best explainedby the following mechanisms: as shown in FIGS. 1A-1D, simultaneoussympathovagal discharges are associated with increased BP (sympatheticeffect), but reduced HR (parasympathetic effect). Simultaneoustermination of these two activities caused a sudden loss of sympathetictone that reduced cardiac contraction and allowed peripheralvasodilatation. A sudden loss of parasympathetic tone allowedinstantaneous heart rate acceleration, which transiently reducesventricular filling and stroke volume. If simultaneous SGNA-VNAtermination is followed by postural changes, then dramatic drops of BPand pulse pressure are observed.

There were significant similarities between the results of this Exampleand that found in human muscle sympathetic nerve activity (MSNA) studiesduring tilt table testing. Typically, upright tilt immediately increasedMSNA. Further, an acute reduction of MSNA and BP was observed inpatients with vasovagal syncope, but not in the controls. These findingsare similar to those observed in Group 1 dogs, in which abrupttermination of SGNA was associated with an abrupt drop in BP. Theseresults support the hypothesis that the final trigger for orthostatichypotension is sympathetic nervous system inhibition.

In the above-described canine model, Group 2 dogs also had intermittentreduction of BP, although not as severe as in Group 1 dogs. Typically,elevated BP triggers a large increase of SGNA and a reduction of BP.Continuation of SGNA during BP reduction is similar to that found insome patients with vasovagal syncope.

Contribution of Vagal Nerve

In these Examples, VNA (or lack thereof) seems to be important in BPcontrol. For example, simultaneous activation of VNA in Group 1 dogs maycounterbalance the effects of SGNA and help maintain a relatively normalHR. These findings suggest that SGNA is the primary phenomenon whereasVNA is the secondary phenomenon that counterbalanced SGNA for BP and HRcontrol. Abrupt termination of VNA allowed HR to increase, which leadsto increased cardiac output and normalization of BP after transientorthostatic hypotension. Absence of VNA in Group 2 dogs implies thatsympathetic tone alone controls the BP changes through vasoconstriction,vasodilation, and HR modulation. The differential patterns of VNA inthese two groups of dogs suggest that more than one mechanism plays arole in the development of intermittent hypotensive episodes in dogs.The importance of VNA in hypotensive episodes in each dog is complicatedby the fact that the grouping of dogs may change overtime. In addition,due to the complex physiology associated with vagal nerve activation,quantitative analyses using integrated vagal nerve activity may not bean optimal method for assessing vagal tone.

Beta 2 Receptor as a Potential Therapeutic Target for PosturalHypotension

It was further hypothesized that if hypotension occurs after thewithdrawal of prolonged sympathovagal firing, then reducing thefrequency and intensity of nerve firing may reduce the instances ofhypotension. Studies in renal sympathetic nerves showed that stimulatingprejunctional β2-adrenoceptors facilitates norepinephrine release. Aprevious clinical study showed that therapy with carvedilol causedsignificant decreases in systemic and cardiac norepinephrine spillover,an indirect measure of norepinephrine release. The authors of thisprevious study concluded that that carvedilol caused itssympatho-inhibitory effect by blocking peripheral, prejunctionalβ-adrenergic receptors. If the latter hypothesis is true, thencarvedilol and ICI, both which block prejunctional β2-adrenoceptors,should reduce autonomic nerve activity and prevent orthostatichypotension. This was not borne out in the instant Example; in fact, ICIled to an average increase in stellate and vagal nerve firing andcarvedilol increased stellate firing though it had no impact on vagalfiring. Furthermore, there is a large variation of nerve dischargeresponses to these drugs, suggesting large differences between dogs.While none of these drugs consistently reduce nerve firing, ICI did leadto an overall increase in BP by eliminating the hypotensive episodes.These findings are best explained by the effects of ICI on vascular β2adrenoceptors. Previous work has shown that the β2 on blood vesselsmediate vasodilation; therefore, blockade of these receptors through ICI(a β2 blocker) would be expected to cause vasoconstriction and thusincrease BP. A previous study in a rat model of orthostatic hypotensionshowed that ICI had a tendency of improving orthostatic symptoms, butthe authors did not show a definite beneficial effect. Although studiesin humans have shown that ICI (in doses up to 80 mg orally) does notalter BP or heart rate, that study did not perform continuous BPmonitoring. The postural hypotensive episodes may not have been detectedin that study. The results of the instant Example suggest that in thecanine model, ICI may be an effective therapy for orthostatichypotension.

Anatomical Basis of SGNA-VNA Coordination

A study to quantitate the amount of TH-positive (catecholamineproducing) nerve structures within the cervical and thoracic vagal nervewas conducted. The results showed a large variation of sympathetic nervecontent among dogs. These findings suggest that if a greater sympatheticcomponent is present in the vagal nerve, then it is more likely that theVNA will occur simultaneously with SGNA. Therefore, the thoracic vagalnerves of dogs from the present Example were studied, as well as thosefrom previous studies, to determine the quantity of sympatheticcomponent in the thoracic vagal nerve. Only a very weak, althoughsignificant, correlation between sympathetic nerve staining in the vagalnerve and SGNA-VNA coordination was found. Furthermore, there isevidence of changing coordination patterns over a 5-month period in dogswith prolonged monitoring. These findings suggest a combined anatomicaland physiological mechanism for SGNA-VNA coordination.

CONCLUSIONS

Coordination between SGNA and VNA is important in determining the BP ofambulatory dogs. Simultaneous SGNA-VNA activation and withdrawal play animportant role in postural hypotension. The SGNA-VNA correlation is onlypartially determined by the amount of sympathetic nerve structures inthe thoracic vagus.

In view of the above, it will be seen that the several advantages of thedisclosure are achieved and other advantageous results attained. Asvarious changes could be made in the above methods without departingfrom the scope of the disclosure, it is intended that all mattercontained in the above description and shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

When introducing elements of the present disclosure or the variousversions, embodiment(s) or aspects thereof, the articles “a”, “an”,“the” and “said” are intended to mean that there are one or more of theelements. The terms “comprising”, “including” and “having” are intendedto be inclusive and mean that there may be additional elements otherthan the listed elements.

What is claimed is:
 1. A method for treating orthostatic hypotension in a subject in need thereof, the method comprising administering a therapeutically effective amount of a β2-adrenoceptor antagonist to the subject, wherein the β2-adrenoceptor antagonist is 3 (isopropylamino)-1-[(7-methyl-4-indanyl)oxy]butan-2-ol.
 2. The method of claim 1 wherein the subject is administered from about 1 μg/kg/hr to about 5 μg/kg/hr of the β2-adrenoceptor antagonist for a period of about 7 days.
 3. The method of claim 1 wherein about 10 mg to about 40 mg of the β2-adrenoceptor antagonist is orally administered to the subject.
 4. The method of claim 1 wherein the subject is an elderly subject.
 5. A method for treating dizziness resulting from orthostatic hypotension in a subject in need thereof, the method comprising administering a therapeutically effective amount of a β2-adrenoceptor antagonist to the subject, wherein the β2-adrenoceptor antagonist is 3 (isopropylamino)-1-[(7-methyl-4-indanyl)oxy]butan-2-ol.
 6. The method of claim 5 wherein about 1 μg/kg/hr to about 5 μg/kg/hr of the β2-adrenoceptor antagonist is administered to the subject for a period of about 7 days.
 7. The method of claim 5 about 10 mg to about 40 mg of the β2-adrenoceptor antagonist is orally administered to the subject. 